1. Field of the Invention
The subject invention is directed toward a unitized seal for a rotary shaft, and more particularly toward such a seal which prevents leakage and infiltration while an end of the shaft reciprocates axially during rotation.
2. Description of Related Art
In some rotating shaft applications, it is necessary for an exposed end of the shaft to slide axially, i.e., telescopically, relative to the remainder of the shaft. By way of example, a typical prior art differential includes a pinion shaft having a telescopic exposed end which attaches to the rear universal joint of a drive shaft. The telescopic pinion shaft is supported in the differential housing by a pair of roller bearings which must be continuously bathed in lubricating oil contained within the differential housing. A shaft seal is disposed between the pinion shaft and the housing to prevent escape of the lubricating oil and prevent foreign matter infiltration.
According to the prior art, various shaft seal configurations have been proposed to accommodate the axial sliding movement of a telescopic rotary shaft. One common approach has been to position the seal so that it does not contact the telescopic end of the shaft. However this leaves the sliding connection (usually a spline) exposed to the elements. The unprotected sliding joint is thus prone to corrosion and contamination.
Another approach has been to machine a seal running surface on the telescopic end of the shaft, against which the primary sealing surface of the flexible annular sealing member can run. However, this approach also has certain undesirable characteristics. For example, it requires precision machining over a length of the telescopic end of the shaft, and in some cases also increases the length of the telescopic end of the shaft.
Furthermore, the combined rotary and axial forces imposed on the primary sealing surface of the flexible annular sealing member lead to rapid wear.